Pump plunger cup



Aug; 31, 1954 1.510111% EI'AL 2,687,845

- 'PUMP PLUNGER CUP Filed June 30, 1950 2 Sheets-Sheet 1 INVENTORS Jy/v 3, YOU/V6 WJLBUR 8. Wm RTON Ire.

Aug; 31, 1954 J. 5. YOUNG EI'AL PUMP PLUNGER CUP Filed June 30, 1950 2 Sheets-Sheet 2 I I l I INVENTORS nTOH/V 5 You/v6 WILBUR B. WHA RToN, 07a.

ATTORNEY Patented Aug. 31, 1954 PUMP PLUNGER CUP John S. Young, Hawthorne, and Wilbur B. Wharton, Jr., East Paterson, N. J assignors to Hawthorne Rubber Manufacturing Corporation, Hawthorne, N. J., a corporation of New Jersey Application June 30, 1950, Serial No. 171,454

7 Claims. (Cl. 230172) This invention relates to an improved, novel, plunger cup for apparatus such as air pumps and liquid displacement spray guns of the reciprocating type. More particularly the invention relatesto a plunger cup of the indicated type which pression zone of the barrel, the relaxed diameter is made of rubber and, rubber-like materials, such materials including therein lubricating material so that the plunger cup is self-lubricating. The term rubber as used hereinafter includes natural and synthetic rubber, and also rubber-like materials.

The plunger cup of the invention is designed toreplace leather plunger cups which have long been used in air pumps and liquid displacement spray guns. Such leather cups are disadvantageous, since the lubricant in such cups has a tendency to dry out, thereby rendering the cups brittle and thus not able to displace air efliciently. Furthermore, such leather plunger cups are difficult to assemble into the pump barrels, and assembly operations are frequently interrupted due to particularly diflicult assembly operations with some of the leather cups. In addition, each plunger cup of the present invention is inherently operative when assembled in a pump barrel, whereas frequently leather cups must be reshaped and reassembled in the pump before they will operate. a i

It is accordingly among the objects of the invention to provide a pump plunger cup of improved design, and of improved fluid displacing eiiiciency, such cup being made of rubber and rubber-like materials and incorporating in it lubricating material so that the cup is permanently self-lubricating.

A further object of the invention resides in the provision of a pump plunger of the indicated type, such cup having a design such that maximum barrel wall sealing action under compression is attained with a minimum of barrel wall contact of the cup on release of pressure in the pump and retraction of the plunger.

Yet another object of the invention in a specific preferred embodiment, lies in the provision of a pump plunger cup of the indicated type which has a substantially flat inner annular zone a and an outer annular portion, such outer portion when relaxed lying generally on the frustum of a cone of large apex angle, the outer edge of such outer zone lying generally at right angles to the elements of the aforesaid cone.

Still a further object of the invention resides in the combination of the plunger cup of the above indicated type with a pump barrel, the cup having its concave surface facing the comof the cup, that is, the diameter of the cup before assembly in the pump barrel, and. the inner diameter of the barrel being so related that the cup is easily inserted into the barrel without the use of jigs or guides and that the cup, when thus assembled and substantially relaxed when the plunger is at rest, contacts the barrel at the outer edge portion of the cup only but that on the forward compression stroke the entire outer edge of the cup is in contact with, or substantially in contactwith, the pump barrel in sealing relationship therewith.

These and further objects of the invention will be more readily apparent upon consideration of the following disclosure or a preferred embodiment of the pump plunger cup of the invention, and of the combination of such cup with a pump cylinder barrel.

In the accompanying drawings which form a part of the specification:

Figure 1 is a view in plan of a pump plunger cup made in accordance with the invention, the concave side of the cup lying upwardly, the cup being in relaxed condition unassembled in the pump barrel;

Figure 2 is a view in diametral section through such pump plunger cup, the section being taken along the line 2-2 in Figure 1;

Figure 3 is a view in vertical cross-section through a pump cylinder and the pump plunger cup and stem therefor, such parts being shown in position for the assembling of the plunger cup in the pump barrel or cylinder} Figure 4 is a view in vertical cross-section through the pump cylinder with the plunger cup assembled therein, the plunger cup being shown in the condition which it assumes on the compression stroke;

Figure 5 is a view in vertical cross-section, similar to Figure 4, through the pump cylinder showing the condition of the pump plunger cup on the idle or return stroke thereof; and

Figure 6 is an enlarged fragmentary View of the pump plunger cup at the wall of the pump barrel, the figure showing in solid lines the cup in the condition which it assumes during a compression stroke, and in dash lines the substantially relaxed condition which it assumes when theplunger is on the idle or return stroke.

The pump plunger cup, in one preferred embodiment thereof, is shown in Figures 1 and 2, where it is designated generally by the reference character 2. Such cup 2 has, as shown, a fiat central annular portion 4, portion 4 having centrally therethrough, the vertical stem receiving hole 6. Disposed radially outwardly of the central portion :3 is the frusto-conical edge portion 3, the upper and lower surfaces l and 62 of which are parallel with each other, as shown. The outer rim of portion 8 is disposed, in the embodiment shown, at right angles to the radial elements of surfaces i0 and [2. This brings the edge it of the upper surface [0 of the cup which, of course, is circular in the embodiment shown, radially inwardly of the outer lower edge portion it of lower surface l2 of the cup. The portion of the cup may be defined as lying along. a frustum of a first cone, and the rim M may be defined as lying along a frustum of a second cone, the apices of the two cones lying on opposite sides of the cup, and the elements of the frustum of the second cone lying generally at right angles to the elements of the frustum of the first cone. In the preferred embodiment of cup shown, the dimension h equals the thickness. of the. annular zone l, which means that edge it. lies. in the plane of the upper surface. of zone 4'.

Simply by way of illustration and definition, and not for purposes of limitations beyond those. required by the scope of the claims, there are given the following dimensions of a typical. pump plunger cup of the type illustrated, when. such cup is in its relaxed state, unassembled in the. pump barrel. Such cup is designed for use in a pump barrel having an inner diameter of one inch; In such illustrative embodiment the overall diameter D of the cup is one and inches. The diameter d of the cup from one edge ill to the other is %-2- inch. The upper diameter d of the central annular portion 4 is inch, whereas the lower diameter l, of such zone is /2 inch. The central annular portionxl has an upper radial: width of d/2, or inch. The frustoeconical edge portion ll has an upper radial width of /2 (dd), or inch. The central annular portion has a lower radial width of 1/2, or /4 inch. The frusto -conical edge portion 8. has a lower radial width of (dl) or inch. The thickness of the central annular portion 4 is, as above noted, inch. This is a large fraction, specifically of the radial width of the central annular portion l. The thickness of the outer annular portion 8, that is, its dimension normal to surface in, is substantially the same as that of portion 4. The diameter d" of the central stem receiving hole 6 is .20 inch. The overall height H of the cup, as viewed in Figure 2, is A. inch, whereas the lower outer edge is of the under surface. H r

lies at a height h which is inch above. the. plane of the bottom surface of portion 4. The elements of surfaces !0 and I2, lie at an angle A of approximately 30 with respect to the horizontal, as the cup is shown in Figure 2. The thickness or the central annular portion of the pump plunger cup and that of the outer annular zone thereof are thus approximately, or on the order of, one-seventh the outer diameter of the plunger cup.

As explained, the cup of the invention is preferably formed of a self-lubricating rubber or rubber-like composition. In a typical embodiment, the cup is formed of a composition containing 25% by weight of refined white petrolatum,

2-3% by weight paraifin compatible with the petrolatum, .the remainder being neoprene (polymerized chloroprene).

The petrolatum and the parafiin, which are both lubricating compositions, are incorporated and mixed with the neoprene by known rubber mixing and masticating methods. The composi-, tion employed is so compounded, treated, and so cured after molding as to be relatively soft, specifically to have a hardness inv the range of from 30-70 durometer onthe Shore A scale, and preferably 40-60 durometer on the same scale. The cup 2 shown in Figures 1 and 2 is formed of synthetic rubber stock, prepared as above, by being molded therefrom in a mold having a cavity complementary to the shape of the relaxed cup asit is shown in such figures. After being molded, as-exp'lained, the cup is cured, preferably in the mold, under such temperatures and for such a period as to give it the desired hardness.

Because of the large amount of lubricating material incorporated in the composition, such composition continually exudes small amounts of the lubricant to the surface of the cup. Thus the cup never becomes dry, constantlyproviding, a thin film of lubricant between the edge of: the cup and the pump barrel.

In Figures. 3-6, inclusive, the pump plunger; cup 2 is shown incorporated in a hand operated. reciprocating pump of. the type used, for ex? ample, in insect Sprayers. Merely the circular; cylindrical pump barrel is shown, since the in vention is not concerned, with any other aspects; of the pumpand spraying device. The pump, barrel, which is designated 2@,'h2,S an; upper closure member 22 at its upper end, and isprovided at 2 1 with a side outlet valve for the air delivered by the pump. As shown, the pumpis.

provided with a plungerstem 26, at the forward end, of which there is provided, a back washer 281 having a diameter somewhat less. than that of the inner diameter D of the pump barrel, The plunger cup 2 is mounted, as shown, on top of the back washer with the forward end of the, stem 26 extending through the hole 6 in the cup. The cup is retained in place by reason. of-

the iorward upset portion32 of stem 28, the front washer 353, and the split locking ring 34, disposed,

behind the back washer 28. The pump is. pro-r vided with the usual centrally apertured front.

barrel closure member 36, through which, the,

the cup 2 but is less than the outer diameter D of the lower edge of the plunger, cup. As, a result of such construction, the plunger cup may readily be inserted into the lower end of the pump barrel, since the lower edge of the barrel does not contact edge is of. the .cu-p'until such cup has been inserted into the barrel: a distance. which is a substantial portion of the thickness of its This construction allows-the plunger cup;

the surface it. The self-lubricating material of:

which cup 2 is made thereupon allows the cup readily to be thrust into the barrel, and temporarily to assume the condition under compression which is shown in Figure 4.

Upon the thrusting of the stem 26 and cup 2 into the pump barrel,- on a compression stroke, the edge portion 8 of the cup flattens out so that the cup is generally of flat annular shape, as shown in Figure 4. Upon the attainment of such shape of the cup 2, the edge M of the cup contacts completely, or substantially completely, over its entire peripheral surface the inner surface of the barrel of the pump. Such sealing tinues until the end of the compression stroke of the plunger, the outer edge portion 3 of the cup, upon the cessation of such compression stroke, regaining substantially its initial relaxed position. Upon retraction of the plunger and cup, on the air intake stroke, the outer edge is of the under surface of the cup 2 retreats sufliciently from the barrel of the pump, at least in peripherally spaced portions thereof, to allow the ingress of air therepast, as indicated by the arrows in Figure 5. The relationship between the outer edge of the cup 2 and the barrel of the pump is shown somewhat more clearly in Figure 6, where such cup and plunger are shown during a compression stroke of the latter. As there indicated, the relationships of the parts, that is, diameter of the pump barrel, diameter of the upper and outer edges of the cup 2, the thickness of the cup 2, etc., are such that when the outer edge of cup 2 is swung from the substantially relaxed condition shown in dotted lines in such figure, to the sealing, operative, position shown in solid lines, there is sealing contact between the edge M of the cup and the pump barrel over substantially the full extent of such edge It. Such deformation of the cup is effected by the increased pressure of the fluid medium in contact with the forward, concave, face of the cup, plus the frictional contact between the pump barreland the edge of the cup. In the design shown, the radial thrust upon the pump barrel is slightly greater in the vicinity of bottom edge l8 of portion 8 of the cup than it is in the vicinity of upper edge I6 of the cup. This follows naturally from the geometry of the outer edge portion of the cup. When the particular cup, the dimensions of which are specifically given above, is flattened as by resting the cup on a flat surface and pressing a flat member on it with a weight sufficient only to press edge It down to the plane of the top of zone 4, it is found that the average diameter from one edge Hi to the otheris 1.020 inches, and that the average diameter from one edge I8 to the other is 1.0311inches, demonstrating that rim M has sealing contact with the pump barrel over the entire extent of the rim during a compression stroke of the plunger. It is probable that during actual working compression strokes of the plunger the cup will tend to expand radially on its upper surface, so that the sealing effect over the rim I 5 will be even more nearly uniform thereover.

It will be apparent from theabove that when the plunger cup is in substantially relaxed assembled condition, that is, when it lies idle within the pumpbarrel, it exerts only an insignificant force upon the barrel, radially of the latter, by

reason of the contact between the barrel and the edge 18 of the cup, as shown in Figure 6. Because such pressure is small, there is little tendency for the cup to acquire a permanent set in the barrel during long periods of disuse. Further, because of the same small pressure exerted by the cup on the barrel when the plunger is idle, as well as the inherent self-lubricating property of the cup, there is no tendency of the cup to bond temporarily to the barrel wall, or to leave a deposit of sticky or gummy matter on it, during such periods of disuse.

Although for purposes of illustration we have given definite dimensions of one size of a preferred embodiment of the pump plunger cup and the barrel thereof, it is to be understood that the invention is not to be so limited. It will be ap parent, from the above description of our invention and of the manner in which it operates, that in the broader aspects of the invention the following conditions only must be observed. The back washer 28 must be substantially smaller in diameter than the diameter D of the pump barrel, to allow the ingress of air therepast. In

the embodiment shown washer 28 has a diameter of 61/64 inch, but it is to be understood that the invention is not limited to such dimension. The plunger cup must be thick enough so as not to fold down into such space between the back washer and the pump barrel. The barrel diameter D of the pump must exceed. the inner edge diameter d of the relaxed plunger cup, but must be smaller than the diameter D, that is, the outer edge diameter of the relaxed cup. The radial widths of the surfaces In and if! of the cup when relaxed and the angle A must bear such a relationship to the barrel diameter D that on the compression stroke all or substantially all of the run surface M of the cup sealingly contacts the inner surface of the pump barrel. Further, in order not to introduce an undue amount of friction into the operation of the pump, the radial width of the surface l2 of the plunger cup must not be so large as to impose an unnecessarily large radial force upon the pump barrel in the location of the bottom outer edge of the plunger cup upon the compression stroke.

Although for purpose of illustration we have described and illustrated a preferred embodiment of the pump plunger cup of our invention and its combination with a pump barrel, it is to be understood that such embodiment is illustrative only, and that our invention is capable of considerable variation as to details, both as to the composition of the plunger cup and also as to the relative dimensions of the various portions of the cup and its relationships as a whole with respect to the pump barrel. The invention is, therefore, to be defined by the scope of the claims appended hereto.

We claim as new the following:

1. A pump plunger cup made of rubber, said cup having a fiat central annular portion and an outer annular zone having generally parallel upper and lower surfaces, which outer zone, when the cup is in relaxed condition, is generally of a frusto-conical shape and lies along the side surface of a frustum of a first cone, the radial width of the outer annular zone being at least equal to the radialwidth of the central zone, the thicknesses of the central annular zone and of the outer annular zone being substantially same and each being a large fraction of the radial width of the central zone, the cup having an outer rim portion, which rim portion, when the cup is in relaxed condition, lies along the side surface of a frustum of a second cone, the apices of the frustums of the two cones lying on opposite sides of the cup, the elements of the amass;

frustum of the second cone-f lying generally at right angles to the elements: of the frustum of, the first cone.

2. A pump plunger cup made of rubber, said cup having a flat central annular portion and an outer annular zone having generally parallel up per and lower surfaces, which outer zone, when the cup is in relaxed condition, is generally of a frusto-conical shape and lies along the side surface of a frustum of a first cone, the radial width of the outer annular zone being somewhat greater than the radial width of the central zone, the thicknesses of the central annular zone and of the outer annular zone being substantially the same and each being a large fraction. of the radial width of the central zone, the outer rim, portion of. the cup in relaxed condition lying along the side surface of a frustum of a second cone, the apices of the frustums of the two cones lying on opposite sides. of the cup, the elements of the frustum of the second cone lying, generally at right angles to. the elements of the frustum of the first cone.

3. A pump, plunger cup made of rubber, the cup having a flat central annular portion and an outer annular zone having, generally parallel upper and lower surfaces, which outer zone, when the cup is in relaxed condition, is generally of a,

frusto-conical shape and lies along the side surface of a frustum of a first cone, the radialwidth of the outer annular zone being at least equal to the radial width of the central zone, the thicknesses of the central annular zone and of? the outer annular zone being substantially the same and being on the order of one-seventh the outer diameter of the plunger cup, the cup having an outer rim portion, which rim portion,

when the cupis in relaxed condition, lies along,

the side surface of a frustum of a second cone, the apices of the frustums of the two cones lying on opposite sides of the cup, the elements of the frustum of the second cone lying generally at right angles to the elements of the frustum of the first cone, the plunger cup, when flattened so that its top and bottom surfaces lie in parallel'planes, having the peripheral; surface of its outer rim portion substantially in the form of a circular cylinder coaxial with said,

plunger cup.

4. A self-lubricating pump plunger cup made. of rubber containing a. substantial quantity of. lubricating medium, said cup having a. flat central annular portion and an outer annular zone. having generally parallel upper and, lower surfaces, which outer zone, when the cup is in relaxed condition, is generally of a frusto conical shape, has its upper surface concave, and lies along the side surface of a frustuin of a first cone, the radial width of the outer annular zone being somewhat greater. than. the radial width of the central zone, the thicknesses of the central annular zone and of the outer. annular zone being substantially the same and being on the order of oneseventh the outer diameter of the plunger cup, the cup having an outer rim portion, which rim portion, when the cup is in relaxed condition, lies along the sidesurface of a frustum of a second cone, the apices of the frusturns of the two cones lying on opposite sides of the cup, the elements of the frusturn of the second cone lying generally at right angles to the elements of the frustum of the first cone, the lower, outer, edge of. greater diameter of the cup lying generally in the plane of the upper surface of the central annular portion, the

"H MW frustum of the first cone having an apex angle in the neighborhood of 120?, the plunger cup, when flattened so that its top and bottom surfaces lie in parallel planes, having the peripheral surface of its outer rim portion substantially in the form of a circular cylinder coaxial with said plunger cup.

5. In a fluid displacement reciprocating pump, the, combination comprising a circular cylindrical pump-barrel, av plunger reciprocably mounted in saidbarrel, a cup backing abutment on the plunger, and a plunger cup mounted on the plunger above the abutment and in fluid displacing relationship with the barrel, said plunger cup being made of rubber, said cup having a flat central annular-zone and an outer annular zone of frusto-conical configuration, the thicknesses f the two zones being substantially equal and each being a large fraction of the radial width of the central zone, said outer zone being concave toward the upper, airdeli-veri-ng end, of the pump barrel, the radial width of the outer annular zone being'atleast equal to the radial width of the central zone, the upper and lower surfaces of the frusto-conical zone-being generally parallel, the outer annular zone-0f the cup when the cup is relaxed generally lying along the side surface of a frustum of a first cone, the cup having an outer rim, which outer rim when the cup is in said relaxed condition lies generally along the side surface of the frustum of a second cone, the apices of the frustums of the two cones lying on opposite sides of the cup, the elements of the frustum of the second cone lying generally at right angles to the elements of the frustum of the first, cone, the abutment being in contact with that side of the plunger cup which is convex when relaxed, the abutment being of a diameter substantially less than the inner diameter of the pump barrel, in its relaxed state the cup having its smaller diameterediportion at the rim less than, and thus spaced from, the inner diameter of the pump barrel, and its larger diametered portion of the rim in right contact with thepump barrel, whereby on the compression strokes of the plunger the outer rim of the cup lies substantially completely in sealing contact with the inner surface of the pump barrel, and on the return stroke of the plunger most of the outer rim of the cup is relieved from contact with the inner surface of the pump barrel.

6. In a fluid displacement reciprocating pump, the combination comprising a circular cylindrical pump barrel, a plunger reciprocably mounted in said barrel, a back washer on the plunger, and a plunger cup mounted on the plunger above the back washer in fluid displacing relationship with the barrel, said plunger cup being made of rubber, said cup having a fiat central annular zone and an outer annular zone of frusto-conical configuration, the two such zones being of substantially the same thickness, said thickness being a large fraction of the radial width of the central zone, said outer zone concave toward the upper, air delivering end, of the pump barrel, the radial widthof the outer annular zone somewhat exceeding the radial width of the central zone, the upper, and lower surfaces of the frusto-conical zone being generally parallel, the outer annular zone of the cup when the cup is relaxed lying along the ,side surface of a frustum of a first cone, the cup having an outer rim, which outer rim when the cup is in said relaxed condition lying generally along the side surface of the frustum of a second cone, the apices of the frustums of the two cones lying on opposite sides of the cup, the elements of the frustum of the second cone lying generally at right angles to the elements of the frustum of the first cone, the back washer being in contact with that side of the plunger cup which is convex when relaxed, the back washer being of a diameter substantially less than the inner diameter of the pump barrel, in its relaxed state the cup having its smaller diametered portion at the rim less than, and thus spaced from, the inner diameter of the pump barrel, and its larger diametered portion at the rim in light contact with the pump barrel, whereby on the compression strokes of the plunger the outer rim of the cup lies substantially completely in sealing contact with the inner surface of the pump barrel, and on the return stroke of the plunger most of the outer rim of the cup is relieved from contact with the inner surface of the pump barrel.

7. In a fluid displacement reciprocating pump, the combination comprising a circular cylindrical pump barrel, a plunger reciprocably mounted in said barrel, a back washer on the plunger, and a self-lubricating plunger cup mounted on the plunger above the back washer in fluid displacing relationship with the barrel, said plunger cup being made of rubber containing a substantial amount of lubricant, said cup having a flat central annular zone and an outer annular zone of frusto-conical, configuration, the two such zones being of substantially the same thickness, said outer zone being concave toward the upper, air delivering end, of the pump barrel, the radial width of the outer annular zone somewhat exceeding the radial width of the central zone, the thickness of the central annular zone and of the outer annular zone .10 being a large fraction of the radial width of the central zone and on the order of one-seventh the outer diameter of the plunger cup, the upper and lower surfaces of the frusto-conical zone being generally parallel, the outer annular zone of the cup when the cup is relaxed lying along the side surface of a frustum of a first cone, the cup having an outer rim, which outer rim when the cup is in said relaxed condition lying generally along the side surface of the frustum of a second cone, the apices of the frustums of the two cones lying on opposite sides of the cup, the elements of the irustum of the second cone lying generally at right angles to the elements of the frustum of the first cone, the back washer being in contact with that side of the plunger cup which is convex when relaxed, the back washer being of a diameter substantially less than the inner diameter of the pump barrel, in its relaxed state the cup having its smaller diametered portion at the rim less than, and thus spaced from, the inner diameter of the pump barrel, and its larger diametered portion at the rim in light contact with the pump barrel, whereby on the compression strokes of the plunger the outer rim of the cup lies substantially completely in sealing contact with the inner surface of the pump barrel, and on the return stroke of the plunger most of the outer rim of the cup is relieved from contact with the inner surface of References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,338,765 Brandt- May 8, 1920 1,511,971 Hunter Oct. 14, 1924 1,673,440 Brinton June 12, 1928 2,455,946 Peters, et a1. Dec. 14, 1948 

